Modification process using N-chloro-thiosulfonamide and rubber

ABSTRACT

Chlorothio-sulfonamide modified rubbery terpolymers, such as chlorothio-sulfonamide modified EPDM rubbers, have utility in a variety of applications. For example, such modified rubbers can be utilized in the sidewalls of pneumatic tires. Such modified rubbers are prepared by reacting a terpolymer of ethylene, an α-olefin containing from 3 to 6 carbon atoms, and a non-conjugated diene containing from 6 to 12 carbon atoms with a N-chlorothio-sulfonamide. The present invention is based upon the unexpected finding that the rate of this reaction can be greatly accelerated by conducting it in the presence of a saturated aliphatic carboxylic acid containing from 6 to 30 carbon atoms, such as stearic acid. The present invention accordingly disclosed in a method of preparing a N-chlorothio-sulfonamide modified terpolymer by reacting a terpolymer of ethylene, an α-olefin containing from 3 to 6 carbon atoms and a non-conjugated diene containing from 6 to 12 carbon atoms with a N-chlorothio-sulfonamide; the improvement which comprises conducting the reaction in the presence of at least one saturated aliphatic carboxylic acid containing from 6 to 30 carbon atoms.

This is a Continuation of Application Ser. No. 07/108,654, filed on Oct.15, 1987 now issued as U.S. Pat. No. 4,820,780.

BACKGROUND OF THE INVENTION

Mixtures or blends of low-unsaturation rubbery polymers with highlyunsaturated rubbery polymers are of practical importance because of thesuperior ozone resistance imparted to the blend of the low-unsaturationrubber. Unfortunately, the presence of the low-unsaturation rubber alsoaffects the mechanical and hysteresis characteristics of thevulcanizates in an adverse manner, as manifesed by lower tensilestrength and modulus values, and by higher dynamic heat build-up andpermanent set. These undesirable phenomena are generally the result ofthe mutual insolubilities of the two types of rubber, the substantiallyslower cure rate of the low-unsaturation rubber, and the greateraffinity of the typiaally polar curatives for the high-unsaturationrubber. As a net result, the vulcanized blend is a heterogeneousdispersion of largely uncured low-unsaturation rubber in well curedhigh-unsaturation rubber. The degraded mechanical and hysteresisproperties caused by this unbalanced cure severely limit, or preclude,the use of such blends in articles subjected to severe servicerequirements such as tires. A process for improving the physical anddynamic properties of such rubbery polymer vulcanized blends is ofconsiderable commercial practical importance.

It is, therefore, an object of this invention to provide a modifiedrubbery polymer having a low degree of unsaturation, a process for itspreparation and composites of blends of such mdified rubbery polymerwith high-unsaturation rubbery polymers.

U.S. Pat. Nos. 3,915,907 and 3,970,133 disclose a rubbery compositionwhich is comprised of an admixture of a rubbery terpolymer of ethylene,α-olefin containing 3 to 6 carbon atoms and a non-conjugated dienecontaining 6 to 12 carbon atoms with an N-chlorothio-sulfonamide of theformula: ##STR1## wherein the mole ratio of saidN-chlorothio-sulfonamide to unsaturated sites in said terpolymer is inthe range of about 0.06/1 to about 1/1, where R¹ and R² are selectedfrom the group consisting of alkyl radicals having 1 to 20 carbon atoms,aralkyl adicals having 7 to 20 carbon atoms, alkaryl radicals havingfrom 7 to 20 carbon atoms, and haloaryl radicals having 6 to 10 carbonatoms an where R¹ is also selected from radicals having the formula:##STR2## where R³ and R⁴ are individually selected from said alkyl,aralkyl, and haloaryl radicals and where R³ and R⁴ can be joinedtogether to represent radicals selected from --CH₂ --_(n), where n is aninteger of 4 to 7, and --CH₂)₂ O--CH₂ --₂.

U.S. Pat. Nos. 3,915,907 and 3,970,133 disclose several techniques whichcan be utilized to incorporate chlorothio-sulfonamides into rubberyterpolymers. One such method involves addition of thechlorothio-sulfonamide to a solution of the polymer in an inert organicsolvent such as heptane, hexane, tetrachloroethylene, cyclohexane,methyl cyclohexane, chloroform, benzene or toluene. More polar solventsare preferred since they increase the rate of formation of polymer boundadduct. For example, adduct formation occurs much more rapidly inchloroform as a solvent than in hexane. A mixture of nonpolar solventwith a highly polar solvent may be used advantageously. For example, amixture of 40 volumes of hexane and 1 volume of acetic acid can producesusstantially faster adduct formation as compared to hexane alone.Furthermore, the rate of adduct formation can apparently be markedlyimproved by contact or catalysis with anhydrous zinc chloride.

A second method comprises swelling a solution of thechlorothio-sulfonamide into the polymer using the same type of solvents.Preferably, the solvent/polymer ratio is selected so that essentiallyall th solvent is taken up by the polymer. For this process, it ispreferable that the polymer is first prepared in the form of smallchunks, or crumbs, and the solvent then added.

A third technique comprise directly milling the chlorothio-sulfonamideinto the polymer by means of an internal mixer (Banbury or extrudertype) or an open roll mill. For direct mixing, it is advantageous tosuspend or dissolve the chlorothio-sulfonamide in a relatively inertmedium suhh as mineral oil or chlorinated paraffin in order to improvedispersion as well as minimize hydrolysis by atmospheric moisture.

In practice it has proven to be difficult to modify rubbery elastomerswith N-chlorothio-sulfonamides due to slow reaction rates. For thisreason, techniques for accelerating the reaction ofN-chlorothio-sulfonamides and rubbery terpolymers, such as EPDM rubbers,have been sought.

SUMMARY OF THE INVENTION

This invention discloses a technique for greatly accelerating the rate awhich rubbery terpolymers can be modified withN-chlorothio-sulfonamides. The technique of this invention simplyentails carrying out such reactions in the presence of a saturatedaliphatic carboxylic acid containing from 6 to 30 carbon atoms.Accordingly, the present invention specifically reveals in a method ofpreparing a N-chlorothio-sulfonamide modified terpolymer by reacting aterpolymer of ethylene, an α-olefin containing from 3 to 6 carbon atoms,and a non-conjugated diene containing from 6 to 12 carbon atoms with aN-chlorothi-sulfonamide; the improvement which comprises conducting thereaction in the presence of at least one saturated aliphatic carboxylicacid containing from 6 to 30 carbon atoms.

DETAILED DESCRIPTION OF THE INVENTION

U.S. Pat. Nos. 3,915,907 and 3,970,133, both of which are incorporatedherein by reference in their entirety, disclose techniques for modifyingrubbery terpolymers with N-chlorothio-sulfonamides. The presentinvention is practiced by simply carrying out such a modification in thepresence of a saturated aliphatic carboxylic acid containing from 6 to30 carbon atoms.

The N-chlorothio-sulfonamides utilized in this invention to modifyterpolymers have the structural formula: ##STR3## where R¹ and R² areselected from the group consisting of alkyl radicals having 1 to 20carbon atoms, aralkyl radicals havig 7 to 20 carbon atoms, alkarylradicals having from 7 to 20 carbon atoms, and haloaryl rdicals having 6to 10 carbon atoms and where R₁ is also selected from radicals havingthe formula: ##STR4## where R³ and R⁴ are individually selected fromsaid alkyl, aralkyl, and haloaryl raiicals and where R³ and R⁴ can bejoined together to represent radicals selected from --CH₂ _(n), where nis an integer of 4 to 7, and --CH₂)₂ O--CH₂ ₂. In theseN-chlorothio-sulfonamides, R¹ and R² are preferably selected from alkylradicals having 1 to 6 carbon atoms, phenyl radicals, monoalkylsubstituted phenyl radicals having from 7 to 10 carbon atoms anddialkylsubstituted phenyl radical having from 8 to 11 carbon atoms. Mostpreferably R¹ and R² are radicals selected from the group consisting ofmethyl groups, ethyl groups, propyl groups, butyl groups, phenyl groups,para-tolyl groups, and p-chlorophenyl groups.

Representative of the radicals suitable for R¹ are radicals selectedfrom methyl, tert-butyl, cyclohexyl, 2-eicosyl, benzyl,2-(p-n-undecylphenyl)-2-propyl, phenyl, 1-naphthyl, p-tolyl,3-ethyl-4-(n-dodecyl)phenyl, p-chlorophenyl and3-chloro-4-(n-butyl)phenyl radicals.

Representative of radicals suitable for R² are methyl, tert butyl,1-eicosyl, cyclohexyl, benzyl, 1-(p-n-dodecylphenyl)-1-ethyl, phenyl,1-naphthyl, m-tolyl, 3,4-di-(n-heptyl)phenyl, p-bromophenyl and3-chloro-4-(n-butyl)phenyl radicals.

Representative examples of N-chlorothio-sulonamides which can be used inthe present invention are N-chlorothio-N-methylmethanesulfonamide,N-chlorothio-N-methylbenzenesulfonamide,N-chlorothio-N-methyl-p-toluenesulfonamide,N-chlorothio-N-ethyl-p-toluenesulfonamide,N-chlorothio-N-methylethanesulfonamide,N-chlorothio-N-phenyl-p-toluenesulfonamide,N-chlorothio-N-(2-propyl)methanesulfonamide,N-chlorothio-N-(1-propyl)-p-chlorobenzenesulfonamide,N-chlorothio-N-phenylmethanesulfonamide,N-chlorothio-N,N',N'-trimethylsulfamide,N-chlorothio-N-methyl-N',N-(pentamethylene) sulfamide,N-chlorothio-N-methyl-N', N-diethylsulfamide andN-chlorothio-N-phenylbenzenesulfonamide.

Chlorothio-sulfonamides suitalle for use in the present invention, aswell as their preparation, have further been described in the patentliterature. For example, West German DPS 1,156,403, which isincorporated herein by reference in its entirety, shows the preparationof chlorothio-sulfonamides by reaction of a sulfonamide with SCl₂ in thepresence of an organic aci acceptor. West German DPS 1,101,407 shows thepreparation of chlorothio-sulfonamides from N,N'-dithiobis(sulfonamides)and chlorine or sulfuryl chloride. The chlorothio-sulfonamides of thepresent invention canbe prepared by analogous procedures.

In the practice of this invention, rubbery terpolymers with lowunsaturation applicable to the inventive process are terpolymers ofethylene, an α-olefin and at least one non-conjugated diene, whereinonly one double bond of the diene enters into the polymerizationprocess, and wherein the diene is incorporated to the extent of about0.1 to about 1.0 moles per kilogram of polymer. Various α-olefinscontaining 3 to 6 carbon atoms can be used representative of which arepropylene, 1-butene, 1-pentene, and 1-hexene. Propylene is preferred.Such types of rubbery terpolymers are well known and can conveniently beprepared by addition polymerization of the monomers in the presence of acoordination or Zeigler-type catalyst complex.

Peferably, the low unsaturation rubbery terpolymer is anethylene-propylene diene terpolymer (EPDM) where said terpolymercomprises a mole ratio of ethylene to propylene in the range of about30/70 to about 70/30 and contains about 0.1 to about 0.8 mole ofnon-conjugated diene termonomer per kilogram of polymer. Preferred arenon-conjugated dienes having 6 to 12 carbon atoms suh as 1,4-hexadiene,dicyllopentadiene, 5-ethylidene-2-norbornene, 5-methylene-2-norbornene,4,7,8,9-tetrahydroindene, and 1,5-cyclooctadiene.

The amount of N-chlorothio-sulfonamide needed to modify a giventerpolymer depends upon a number of factors including the specificnature of the terpolymer being modified and the characteristics desiredfor the final vulcanizate. As a general rule from about 0.1 to about 10phr (parts per hundred parts of rubber) of the N-chlorothio-sulfonamidewill be utilized. In most cases it willbe preferred to utilize fromabout 0.5 to 5 phr of the N-chlorothio-sulfonamide modifier. As ageneral rule, the molar ratio of modifier to unsaturated sites in thepolymer will be within the range of about 0.03/1 to about 1/1, but ispreferably in the range of about 0.15/1 to about 0.8/1 and morepreferably about 0.2/ to about 0.7/1. With some EPDM polymers, the useof high ratios can lead to polymer viscosity increases which makeprocessing exceedingly difficult or even practically unmanageable. It isexpected that, recognizing this, those having ordinary skill in thepolymer compounding art will use a ratio which enhances characteristicsof the final vulcanized blend without detrimentally increasing polymerviscosity beyond the point of ease of processability.

The amount of saturated aliphatic carboxylic acid needed in themodification procedures of this invention will generally be within therange of about 0.1 to 10 phr. It will normally be preferred for theamount of saturated aliphatic carboxylic acid utilized to be within therange of 1 to 6 phr with 3 to 4 phr being most preferred. The saturatedaliphatic carboxylic acids which are utilized in the modificationprocedures of this invention will contain from 6 to 30 carbon atoms.Such saturated aliphatic carboxylic acids will preferably contain from10 to 28 carbon atoms. The most preferred saturated aliphatic carboxylicacids will contain from 12 to 20 carbon atoms. The saturated aliphaticcarboxylic acids tilized will be saturated and will accordingly be ofthe formula C_(n) H_(2n+1) COOH, wherein n is an integer from 5 to 29.Palmitic acid, lauric acid, and stearic acid are representative examplesof saturated aliphatic carboxylic acids of this type. Branched saturatedaliphatic carboxylic acids containing from 6 to 30 carbon atoms, such as2-ethylhexanoic acid, can also be utilized to accelerate themodification reaction.

The modifications of this invention will preferably be carried out in aninternal mixer, such as a Banbury mixer or an extruder. Suchmodifications are carried out by simply mixing the saturated aliphaticcarboxylic acid and the N-chlorothio-sulfonamide modifier throughout therubbery terpolymer being modified. Such modifications are normallyconducted at an elevated temperature which is within the range of 60° C.to about 190° C. It is generally preferable for such modificationprocedures to be carried out at a temperature which is within the rangeof 100° C. to 170° C. with temperatures within the range of 110° C. to160° C. being most preferred.

The saturated aliphatic carboxylic acids utilized in accordance withthis invention accelerate the modification process to the degreenecessary for such modifications to be carried out in extruders havingtypical residence times. For instace, the modification reaction can becarried out at a rate that makes the utilization ofextruders havingresidence times of 90 seconds or even less practical.

Unreacted modifier can react with water to produce hydrochloric acid asa reaction by-product. Hydrochloric acid typically has an adverse effecton extruders and other processing equipment. It also typically has anadvere effect on the properties of the rubber being prepared. For thesereasons, it is usually advantageous to carry out the modificationprocedures of this invention in the presence of an agent which willreact with the hydrochloric acid produced to form a salt. For instance,calcium carbonate can be added which will react with any hydrochloricacid produced so as to form calcium chloride. It is normally desirableto utilize from 0.001 to 1 phr of calcium carbonate in the modificationprocedures of this invention. It will generally be preferred to utilizefrom 0.01 to 0.5 phr of calcium carbonate in such modificationprocedures with the utilization of 0.02 to 0.1 phr of calcium carbonatebeing most preferred.

This invention is illustrated by the following examples which are merelyfor the purpose of illustration and are not to be regarded as limitingthe scope of the invention or the manner in which it can be practiced.Unless specifically indicated otherwise, parts and percentages are givenby weight.

EXAMPLE 1

In this experiment an EPDM rubber was modified withN-chlorothio-N-methyl-benzenesulfonamide (CTMBS) in the presence ofstearic acid. The EPDM rubber utilized in this experiment was DuPontNordel™ 1660 which contains about 66% ethylene, about 28% propylene andabout 5 to 6% 1,4-hexadiene. The modification was carried out in a 420cc stainless steel Brabender Prep Mieer which was equipped with camblades, an oil cooled jacket at 50° C., and a Brabender Model PLD-651microprocessor-controlled drive unit. The Brabender mixer was run at 60rpm. In the procedure utilized, 234 g of the EPDM was initially addedwith 0.05 g of calcium carbonate and 8.2 g of stearic acid. After amixing time of about one minute, the temperature increased from 115° C.to 121° C. and 6.7 g of CTMBS was added. After 40 additional seconds ofmixing time, the temperature had increased to 126° C. at which time 15 gof cyclooctadiene was added as a shortstop (to compete with EPDM forunreacted modifier by formation of a CTMBS-cyclooctadiene adduct).Mixing was continued for 4 additional minutes during which time thetemperature continued to increase to 145° C. The EPDM was then dischargeand cooled in ambient air. The modified EPDM produced was subsequentlyanalyzed for bound adduct content utilizing UV spectroscopic techniques.It was determined that the modified EPDM produced contained 0.076 molesper kilogram of bound chlorothio-sulfonamide adduct.

COMPARATIV EXAMPLE 2

The procedure utilized in Example 1 was used in this experiment exceptthat no stearic acid was initially added. However, 8.2 g of stearic acidwas added in conjunction with the cyclooctadiene as a shortstop system.In this experiment, it was determined that the modified EPDM producedhad a bound adduct content of only 0.025 moles per kilogram.

As can be determined by comparing Example 1 with Comparative Example 2,the presence of stearic acid during the modification procedure greatlyincreased the amount of chlorothio-sulfonamide adducted to EPDM present.In fact, the presence of stearic acid during the modification procedureresulted in a three fold increase in the amount of adduct formed. Thus,it is very apparent that saturated aliphatic carboxylic acids can beutilized to greatly increase the rate at which such modficationreactions proceed.

While certain representative embodiments and details have been shown forthe purpose of illustrating the present invention, it will be apparentto those having skill in this art that various changes and modificationscan be made therein without departing from the scope of the presentinvention.

What is claimed is:
 1. In a method of preparing aN-chlorothio-sulfonamide modified terpolymer by reacting a terpolymer ofethylene, an α-olefin containing from 3 to 6 carbon atoms, and anon-conjugated diene containing from 6 to 12 carbon atoms with aN-chlorothio-sulfonamide; the improvement which comprises conducting thereaction in the presence of at least one saturated aliphatic carboxylicacid containing from 6 to 30 carbon atoms.
 2. A method as specified inclaim 1 wherein the reaction is carried out at a tmperature within therange of 60° C. to 190° C.
 3. A method as specifiediin claim 2 whereinfrom 0.1 to 10 phr of saturated aliphatic carboxylic acids is present.4. A method as specified in claim 3 wherein from 0.1 to 10 phr ofN-chlorothio-sulfonamide is present.
 5. A method as specified in claim 4wherein said saturated aliphatic carboxylic acids contain from 10 to 28carbon atoms.
 6. A method as specified in claim 5 which furthercomprises conducting the reaction in the presence of 0.001 to 1 phr ofcalcium carbonate.
 7. A method as specified in claim 6 wherein saidreaction is conducted at a temperature within the range of 100° C. to170° C.
 8. A method as specified in claim 7 wherein from 1 to 6 phr ofsaturated aliphatic carboxylic acids are present.
 9. A method asspecified in claim 8 wherein from 0.5 to 5 phr ofN-chlorothio-sulfonamide is present.
 10. A method as specified in claim9 wherein said N-chlorothio-sufonamide is selected from the groupconsistigg of N-chlorothio-N-methylmethanesulfonamide,N-chlorothio-N-methylbenzenesulfonamide,N-chlorothio-N-methyl-p-toluenesulfonamide,N-chlorothio-N-ethyl-p-toluenesulfonamide,N-chlorothio-N-methylethanesulfonamide,N-chlorothio-N-phenyl-p-toluenesulfonamide,N-chlorothio-N-(2-propyl)methanesulfonamide,N-chlorothio-N-(1-propyl)-p-chlorobenzenesulfonamide,N-chlorothio-N-phenylmethanesulfonamide,N-chlorothio-N,N',N'-trimethylsulfamide,N-chlorothio-N-methyl-N',N-(pentamethylene) sulfamide,N-chlorothio-N-methyl-N',N-diethylsulfamide andN-chlorothio-N-phenylbenzenesulfonamide.
 11. A method as specified inclaim 1 wherein said N-chlorothio-suffonamide is selected from the groupconsisting of N-chlorothio-N-methylmethanesulfonamide,N-chlorothio-N-methylbenzenesulfonamide,N-chlorothio-N-methyl-p-toluenesulfonamide,N-chlorothio-N-ethyl-p-tolunesulfonamide,N-chlorothio-N-methylethanesulfonamide,N-chorothio-N-phenyl-p-toluenesulfonamide,N-chlorothio-N-(2-propyl)methanesulfonamide,N-chlorothio-N-(1-propyl)-p-chlorobenzenesulfonamide,N-chlorothio-N-phenylmethanesulfonamide,N-chlorothio-N,N',N'-trimethylsulfamide,N-chlorothio-N-methyl-N',N-(pentamethylene) sulfamide,N-chlorothio-N-methyl-N',N-diethylsulfamide andN-chlorothio-N-phenylbenzenesulfonamide.
 12. A method as specified inclaim 8 wherein said saturated aliphatic carboxylic acid contains from12 to 20 carbon atoms.
 13. A method as specified in claim 12 whereinsaid reaction is carried out at a temperature within the range of 120°C. to 160° C. and wherein said N-chlorothio-sulfonamide isN-chlorothio-N-methylbenzenesulfonamide.
 14. A method as specified inclaim 16 wherein said reaction is carried out in the presence of 0.01 to0.5 phr of calcium caroonate.
 15. A method as specified in claim 13wherein said reaction is carried out in the presence of 0.02 to 0.1 phrof calcium carbonate.
 16. In a method of preparing aN-chlorothio-sulfonamide modified terpolymer by reacting a terpolymer ofethylene, an α-olefin containing from 3 to 6 carbon atoms, and anon-conjugated diene containing from 6 to 12 carbon atoms with aN-chlorothio-sulfonamide; the improvement which comprises conducting thereaction in an extruder in the presence of 0.1 phr to 10 phr of at leastone saturated aliphatic carboxylic acid.
 17. A method as specified inclaim 1 wherein the saturated alihhatic carboxylic acid is lauric acid.18. A method as specified in claim 4 wherein the saturated aliphaticcarboxlic acid is lauric acid.
 19. A method as specified in claim 8wherein the saturated aliphatic carboxylic acid is lauric acid.